Five ABC staffers were today ordered to the headquarters of Federal Police in Sydney to be interrogated. The police are investigating allegations that an ABC employee may have leaked sensitive internal memoS to newspaper journalists. Seven others have been informed they're also under suspicion, including the managing director's own press secretary and some senior executives. They'll be interviewed by the AFP next week. It's a mole-hunt that might fit better in a John Le Carre novel than the corridors of the national broadcaster. But what triggered it?

---------Compere: Tony JonesReporter: John Shovelan

JOHN SHOVELAN: The police hunt for a mole within the ABC produced another day of crisis for the corporation's executive.

Angry ABC staff held a stop-work meeting to condemn management for inviting the Australian Federal Police to interrogate their fellow workers.

WOMAN: I mean, you turn up to work and do your job.

You don't expect to have to go to the police for it, really.

MAN: Everyone's very shocked about what's happened.

It seems like the final straw, in some ways.

WOMAN: We're in a bit of shock.

'Cause it just seems so absurd that these people have been taken to the police station.

JOHN SHOVELAN: The police interviews began at nine this morning.

Five staff members were questioned at AFP headquarters in Sydney in the first phase of an investigation which will continue into next week.

One of the suspects grilled by police has been an ABC employee for 40 years.

The police investigation follows an early warning from managing director Jonathan Shier to anyone tempted to leak information.

JONATHAN SHIER, ABC MANAGING DIRECTOR: If you feel you have to say it to members of the press, then please think twice.

JOHN SHOVELAN: But the head of the ABC's audit unit says while he informed Mr Shier, it was his decision alone to call in the police.

DAVID HODGKINSON, ABC GROUP AUDIT HEAD: It's my call as head of ABC Group Audit as to whether it was a serious enough issue to actually report and I determined that this was a very confidential, an internal document.

JOHN SHOVELAN: Mr Hodgkinson said the leaked document was extremely sensitive.

It showed the new ABC structure under Mr Shier could see an increase of 55 new executive positions at an extra cost of $7.5 million.

The Public Sector Union says the document should never have been kept secret.

GRAEME THOMSON, COMMONWEALTH PUBLIC SECTOR UNION: That document deals with the expenditure of public taxpayer-funded dollars for the ABC.

These are dollars that the public has got a right to know about how they're being spent.

JOHN SHOVELAN: The police investigation comes in the same week Mr Shier sacked three of his self-appointed executive team, including Guy Dunstan, the man central to Mr Shier's vision to reshape the corporation.

Police will continue to interview ABC staff about the leaked document on Monday.